1. Field of the Invention
This invention relates to an apparatus and method for detecting inhomogeneities in semi-plastic substances, such as soap bars, through the use of ultrasound.
2. The Related Art
Ultrasound has been used in many fields as a non-destructive, non-invasive testing and diagnostic technique. It has been employed industrially for measuring the thickness of machined parts, monitoring corrosion inside pipes and vessels, finding flaws in welds and castings, and in measuring material properties. In medicine, it is used widely as a diagnostic imaging tool for scanning the abdomen, heart and other areas to detect disease or abnormalities.
A variety of consumer products have been monitored for quality control through ultrasound. For instance, U.S. Pat. No. 4,208,915 (Edwards discloses a method for determining by ultrasonic frequency detection foreign material in food products. A plurality of transducers are disposed in a rotatable cylinder having a liquid conductor. The cylinder having a surrounding flexible wall is compressed against the top surface of food products being transported beneath the cylinder on a conveyor belt. Food items stated to be suitable for examination are meat patties, fish fillets, boneless chicken products and, especially, hamburgers. Typical foreign objects include metal, bone particles, hair and pieces of cloth.
Fluid processed foodstuffs can also be inspected ultrasonically as reported in U.S. Pat. No. 4,384,476 (Black et al.). Among the foodstuffs amenable to inspection by this technique are flowable pasty or comminuted fruits and vegetables, ketchup, ground meats and soups. Also monitorable are aqueous slurries of fruits and vegetables which may be checked for unremoved pits, seeds, stems or even for rotten cores. The method involves transporting the foodstuff through a pipeline that includes an inspection station formed from a light transparent plastic. A curtain of ultrasonic sound is passed through an entire cross-section of the fluid foodstuff passing through the inspection station. Individual transducers are reported to be of a ceramic solid solution of lead zirconate and lead titanate dimensioned such that they oscillate and may be driven at a frequency of approximately 2.25 MHz.
U.S. Pat. No. 4,822,573 quality tests food filled packages subject to spoilage. The inspection method involves shaking each package in an agitation device and downstream therefrom passing the package between a package body thickness limiter immersed in a water tank wherethrough the ultrasound is transmitted. The useful wavelength region is stated to be between 0.5 and 20 MHz.
In the Journal of the American Oil Chemists' Society, 1984, 61(3) 560-564, there has been reported the use of ultrasound to investigate solid fat index dilatation during solidification of oils and fats. A doctoral dissertation has even been written about the technique as it relates to cheese wheys, margarines, and frozen dessert mixes. See Dissertation Abstracts International, B 1972, 33(4) 1604-1605.
Beyond foods, ultrasound has been employed to investigate solids levels in mouthwashes (J. Pharm. Sci., 67(4), 492-6 (1978)) as well as with cosmetic creams (Izv. Vyssh. Uchebn. Zaved., Pishch. Tekhnol., (5), 34-7 (1988)).
Most of the foregoing art has focused upon substrates that are either solids or substantially liquids. The probe of these type materials is a reasonably straight-forward task. Detectors can readily make contact and these materials echo easily interpretable signals. On the other hand, semi-plastic substances are not easily amenable to being probed. Difficulties in contact between probe and substance as well as interpretation of signals arise in this area.
Accordingly, it is an object of the present invention to provide an apparatus and method for detecting inhomogeneities within a semi-plastic substance.
A more specific object of the present invention is to provide an apparatus and method for detecting inhomogeneities such as foreign materials, undesirable phase structures, crystallinity and excess moisture in semi-plastic substances through the use of ultrasound.
A further object of the present invention is to provide an apparatus and method for detecting metal, glass, wood or other such foreign objects in toilet bars containing soap.